This invention relates to cooling and lubricating of an output disk of a toroidal continuously variable transmission and its periphery.
A toroidal continuously variable transmission (T-CVT) disclosed in JP-A-H11-63139 published by the Japanese Patent Office in 1999 discloses a toroidal transmission unit comprising an input disk and an output disk disposed coaxially, and power rollers which transmit power between the input disk and output disk. The T-CVT is often a double cavity type wherein two toroidal transmission units are disposed coaxially, so that power transmission capacity is doubled and so that the thrust forces cancel out as internal forces and do not act on the transmission case when the power rollers are gripped between the input disk and output disk.
In such a double cavity T-CVT, the input disks of both toroidal transmission units are disposed at some distance away from each other on a main shaft, and they rotate together with this main shaft. The output disk common to the input disks is rotatable relative to the main shaft between the input disks, and the power rollers are gripped between the input disks and output disk so that power is transmitted between the input disks and output disk.
By forming the output disks of the two toroidal transmission units in one piece, the axial length of the T-CVT can be shortened. The rotation from the engine is transmitted to the input disks via loading cams and transmitted to the common output disk from the input disks via the power rollers, and power is extracted from disk gears provided on the outer circumference of the output disk.
When the output disks of the two toroidal transmission units are formed in one piece as described above, for the cooling of the output disk, lubricating oil is supplied between the main shaft and the output disk from an oil passage in the main shaft through holes formed in a radial direction, and it flows out from both sides of the output disk. However, in this case, the lubricating oil is not discharged smoothly, so the heat exchange efficiency is low, the cooling of the output disk being particularly inadequate within the disk itself.
If the cooling of the output disk is inadequate, the temperature of the oil between the disk and the power rollers rises and a traction coefficient decreases, so not only does the torque transmission capacity decline, but durability is also impaired.
It is therefore an object of this invention to efficiently cool the common output disk of the two toroidal transmission units. It is a further object to efficiently lubricate bearings which support the output disk, and gears which transmit power from the output disk.
In order to achieve above object, this invention provides a continuously variable transmission, comprising a main shaft comprising a lubricating oil passage formed inside thereof, a pair of input disks provided on the main shaft, and rotating together with the main shaft, an output disk being common to the input disks and disposed between the input disks rotatably fitted on the main shaft, and power rollers gripped between the input disks and the output disk. A cooling passage is formed in the output disk, extending from the inner circumference to the outer circumference of the output disk, and lubricating oil in the lubricating oil passage is supplied to the cooling passage via a gap between the main shaft and the output disk.
The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings.